Energy Efficient

Cold Snap Tests High-Performance Homes

At the top of a hill in the Old Port section of Portland, Maine, stands a city landmark: the "Time and Temperature Building." On the roof of the building is a lighted sign displaying — yes — the time and the temperature, alternating with a sponsor's message: "Call Joe."

But you don't need Joe to tell you it's cold in Maine. Last week, the sign's message at dawn, flashing across the waters of the Portland harbor to island communities off shore, has been nothing if not consistent:0°F.

For some New Englanders—and for homeowners in the nation's breadbasket as well—the winter cold snap has brought discomfort, along with worries about the supply and price of heating fuel. But what about the fortunate few who live in high-performance modern houses? Are those buildings living up to their promise in the face of lingering polar air?

In December, JLC featured four advanced high-performance, super-insulated building designs. This week, we talked with homeowners who are living in some houses built following those designs to find out how the homes are coping with this year's record cold.

Wood heat only in Vermont

In Ripton, Vermont, homeowner Chris Pike is living in a house constructed by builder Alex Carver and designed by Belfast, Maine, builder Chris Corson. Aside from a few tweaks—a change in the second-story floor plan and a longer shed addition on the north side—the house is a near replica of the home Corson built in Knox, Maine, featured in the May and June, 2012, issues of the Journal of Light Construction (see "An Affordable Passive House — Part 1," and "An Affordable Passive House Part II"). But Chris Pike's house has the more advanced details described in the JLC feature from December 2013, "Building Above-Code Walls" (subscription required), including a breathable synthetic exterior membrane in place of the fiberboard sheathing used in the earlier example.

Alex CarverChris Pike's house, built by Alex Carver (Northern Timbers Construction), near completion in fall 2013. This winter, says Pike, the house stays comfortable in below-zero weather with one or two firings of the wood stove per day.

Like the Knox house, Corson's earliest Passive House prototype, the Ripton house is designed to be heated with a single, wall-mounted Mitsubishi Mr. Slim air-source heat pump that draws 1800 watts and is rated to supply 12,000 Btu/hr. But that output is under ideal laboratory conditions, not in below-zero degree weather. As it turns out, however, the Pike family isn't using the heat pump. "It got turned on once, when the house was commissioned," says Chris Pike.

Instead, the Pikes are relying on the home's wood stove, a Morso 3112 rated at 30,000 Btu/hr. They light one or two fires a day. "In the evening, my wife might start a small fire in the wood stove after the kids are in bed, just for us to hang out by," says Chris Pike. "And by ten or eleven o'clock the fire goes out and we go to bed. And if it's around 68 degrees when we go to bed, when we get up in the morning, it's usually around 62 or 64. And if it's going to be a sunny day, it's best not to start the wood stove again in the morning, because the sun will heat the house up. Even on these days where it has been 10°F or 5°F outside, the sun brings this place right up to temperature."

"Today," said Pike, "it's sunny and it's 10°F outside. It's 72°F in the house right now at one in the afternoon, and the wood stove was out by 9 o'clock this morning. On days like today where it's bright and sunny, it's almost overkill to have run the wood stove in the morning." With January almost over, Pike says, the family has burned a third of a cord of wood this winter. "We're burning hot fires, and then let them go out," he says. "I've had to empty the ash can maybe twice for this thing, because we just burn so efficiently that there is not a lot of ash left over."

The coldest weather Pike has seen this winter is 20-below-zero one night. The house took it in stride, he says. "We might run the stove a little more in the evening. We might start it at six instead of eight. But it still goes out—we don't run it all night long. And when we get up in the morning, it's still around 62 to 64 degrees.

Bedrooms on the north side of the house run slightly cooler than the sunnier south-facing rooms, Pike notes, but they're still comfortable. "We leave the doors open, and it evens out," he says. "I'm walking around in shorts and a T-shirt, because it's 72 or 73 degrees in here with no heat on." Bottom line, says Pike: "The house has worked great. I can't be happier. I can't say enough about it. It's doing everything it's supposed to be doing."

Out of power in Maine

In Belfast, Maine, residents of the Belfast Cohousing and Ecovillage, whose hybrid SIP and stick-frame homes were built by Alan Gibson and Matt O'Malia of GO-Logic, have been handling the same brutal cold, but with a twist: Their homes lost power for five days at Christmas time after an ice storm downed power lines, cutting power for a wide swath of northern Maine. "And it's an all-electric house," says resident Margie Shannon.

"It was a huge shock to us, because before we moved in here, we lived for 22 years off the grid," says Margie. "Back then we had wood stoves, and propane, and solar panels, and we took care of ourselves."

"We went through an ice storm in 1998 and we survived very well," says Mike Shannon. "We had everything we needed. But when this power outage hit, it was like somebody pulled the rug out from under us. We felt very vulnerable."

"We said, 'Well, now what do we do?'" says Margie.

The Shannons were able to cook meals on a small alcohol stove, and they had a small kerosene lantern for light. But in an airtight house, they worried about carbon monoxide, so they used their backups sparingly, keeping a window cracked. Refrigeration, obviously, was no problem—anything they wanted to keep frozen, they put outside, and as their house cooled down, spoilage of items in the refrigerator wasn't a big worry.

Fortunately, the home performed well. "The week that the power went off, we had a morning that was 15 below zero here," says Mike Shannon. "But the remarkable thing was that all of these houses maintained a temperature from the mid-fifties, close to sixty, for those five days. We felt pretty good about that. These insulated houses performed terrifically." Sitting next to the house's German-made super-windows at night with the house in the fifties and the outdoor temperature at minus 15, Mike says, "I felt no cold coming from those windows at all."

The experience has given the Belfast co-housing community pause for thought. "Our common house is still under construction," says Margie, "and it's delayed because of the weather. Last week there was somebody ice-skating on the foundation slab. But it's actually a good thing, because now we have time to think about what we should do." The co-housing residents, who all get a vote in how the common house will be finished, are now considering whether they ought to equip at least that one building with propane cooking facilities and an emergency generator.

Interestingly, the return of grid power was not the end of the trouble at the Belfast Cohousing community. The 26 occupied units at the community (a few are still being built) have electric hot water tanks, and when Central Maine Power turned on the lights, they all called for power at once and blew a power company fuse. The homes are equipped with power monitors, Mike Shannon says, and at his house, the peak draw can be 6,000 kilowatts when showers, laundry, and dishwashing are happening along with the operation of the heat pump for space heating. Times 30, that's a surge. "CMP has a main fuse out on the pole," says Margie, "and the fuse they had put in was early on, and it was appropriate for four houses. Now we have 26."

As long as the power doesn't go out, however, the Shannons have found their home to be comfortable as well as affordable, summer and winter. "Ours is a 900 square-foot model," says Margie. "The big open-plan kitchen, living, and dining area is half the house, then there are two other small rooms. And we've only ever turned the heat on in the big room."

The Shannons were the first couple to move into the cohousing project, and this is their second winter. In their first year, they spent just under $800 for power, including heat, lights, plug loads, cooking, the heat recovery ventilator, and hot water. But they also have two small photovoltaic panels on their roof, and after credits for the power they produce, their annual electric bill last year was closer to $350. "We made 65% of our electricity," says Margie. "We used 5,500 kilowatt-hours and we made 3,000-something."

Even in the dead of winter, the electric bill isn't a big deal. "This house is a lot cheaper to live in than our old off-the-grid house," says Margie, "because there we had to pay for wood and propane." She ticks off the couple's latest bills (which include a $9 delivery charge regardless of use): "The September bill was $32. The October bill was $24. The November bill was $62. December [including five days with no power] was $134. And then I only have last year's January bill, which was $136. And then it drops right down again."

That's cheap by any standard, and certainly cheap in the context of Maine, where homeowners can pay $1,000 for heating oil more than once a winter. "But since we did have this power outage, now we're looking for ways to have resilient backup," says Mike.

Cramer SilkworthAs temperatures plunged into the single digits, a Brooklyn row house retrofitted to Passive House standards hovered in the mid-sixties to low seventies, using heat for just a single half-hour period in mid-week.

Coasting in Brooklyn

In Brooklyn, New York, meanwhile, Passive House consultant Cramer Silkworth is keeping tabs on a project he completed last year (see Silkworth's blog post, "Polar Vortex in a Passive House? Fuggedaboutit…"). Silkworth displays a graph of the Brooklyn brownstone's temperature through last week's frigid weather, when outdoor temperatures dropped to about 5°F overnight at the coldest point. In the brownstone, the heat—a 2-ton mini-split air-source heat pump—came on only once during the week, for less than an hour, to bump the indoor temperature up from 65°F to 70°F, after which the house coasted. "The heat was only turned on at the point noted," writes Silkworth (see graph). "Other than that, the temperatures are maintained within normal (albeit variable) comfort levels without any heating system (other than the sun and internal sources; that is, passive house principles)."

"It should be noted that the temperature was measured in the living room where the family spends a lot of time," Silkworth admits. "But still," he writes, "I'm amazed."